The Light-Sensitive Hormone Quietly Running Your Energy, Weight, and Cravings

Before insulin, before cortisol, there’s leptin. The master signal no one talks about that tells every other hormone how to function.

Most mornings start quietly.

I’m usually up before the sun, somewhere between 5:30 and 6. The house is still dark, the air feels calm, and if I listen closely, I can hear the birds begin to wake up (super cute). It’s my absolute favorite part of the day. That soft, in-between moment before the world stirs.

And then… the sheepdog hours begin.

Between 6:30 and 7:30, it’s go time. Three kids, shoes that can’t be found, hair that must be braided “just so,” overlapping questions that must be answered simultaneously, and at least one last-minute school project that needs my help. Somehow, breakfast happens too.

It’s a rhythm I that I know I’ll miss someday. But it’s also one that takes energy. Real, steady energy.

That’s where leptin comes in.

Leptin is one of those behind-the-scenes hormones that quietly sets the tone for how the rest of your day will feel. It doesn’t just decide how hungry you are; it tells your brain whether you have enough energy stored, whether you should burn or conserve, whether you can feel calm or need to stay alert. It’s like the body’s morning meeting with the brain: Here’s where we’re at, here’s how we’ll handle the day.

When leptin signaling is clear, you start your day grounded. When it’s scrambled, everything feels harder. Even getting out the door.

Meet Leptin: The Quiet Regulator

The first time I learned about leptin, I pictured it like a quiet messenger bird flying from my fat cells up to my brain, whispering, “You’re safe. You’ve got fuel. You can stop searching for food.”

It’s not a loud hormone. You don’t feel it like adrenaline. You don’t see it like cortisol spikes or insulin crashes. But it’s behind the scenes of everything: hunger, energy, metabolism, even fertility and mood.

Leptin’s job is simple: it tells your brain how much energy you have in storage and what to do about it. If your fat cells are full, it tells your brain, “We’re good…burn energy, move, feel balanced.” If they’re low, it says, “Hold on to everything. Food might be scarce.”

It’s a brilliant system. Until the signals get scrambled.

When the Body’s Messages Get Lost

Not long ago, I was talking with someone who said, “I’m doing everything right…eating clean, exercising…but I still feel like my body’s working against me.”

I hear that a lot with my clients. And it always makes sense once we look closer.

Because it’s rarely about willpower. It truly does come back down to rhythm.

Think about it. Late-night scrolling. Skipping breakfast because you’re not hungry yet. Reaching for a snack between calls just to stay awake. Getting light from screens instead of sunlight.

It’s not bad behavior…it’s just modern life. But it’s also the perfect storm for confusing the body’s signals.

When we’re out of sync, leptin can’t get its message through. Too much insulin from blood sugar swings keeps the “I’m full” signal quiet. Too little melatonin at night keeps the repair system offline. The whole communication network starts to fray.

And that’s when you wake up one day feeling like your body isn’t listening to you. When really, it’s been trying to talk to you all along.

Once we start syncing things back up: morning light before coffee, a real breakfast with protein, fewer screens before bed…the change is undeniable.

People often say, “I finally feel like my body’s on my team again.”

And that’s the shift that changes everything.

The “Neighborhood” of Signals (as I like to call them)

Leptin doesn’t work alone. It shares a wall with insulin. Their receptors sit right next to each other, constantly cross-talking.

When insulin spikes (especially from blood sugar swings) it can muffle leptin’s voice.

And then there’s melatonin (which legitimately works so much magic at night). Melatonin helps sensitize leptin’s receptor, which is one of the reasons evening light exposure is such a problem. When we stare at screens or keep the lights bright after sunset, melatonin never gets its chance to rise. Without that, leptin’s nighttime repair work stalls.

These three: leptin, insulin, and melatonin, form the body’s version of a group text. If one gets disrupted, the whole conversation goes sideways.

We Tend To Think of Health in Silos

Blood sugar over here, sleep over there, hunger and mood in another corner.
But your body doesn’t see it that way. It’s all one network, one feedback loop, one rhythm.

When leptin is off, we crave more, move less, and lose our natural rhythm with food and rest.

When it’s working, everything flows. Energy, appetite, mood, even the quiet confidence that comes from feeling in sync.

That’s what this hormone really is: not a weight-loss hormone, not a hunger hormone, but a trust hormone. It tells your brain that you’re safe enough to burn energy, repair, and let go.

So Where Do You Start?

Start by listening to your rhythm.

Get morning light in your eyes before your phone (or use blue blockers until you can get outside).

Eat breakfast within an hour of waking, with real protein.

Avoid eating too close to bedtime.

And dim the lights when the sun goes down.

None of these things are too dramatic. But they whisper to your biology in the language it understands: safety, stability, trust.

And that’s the language leptin speaks fluently.